Despite an increasing number of US states legalizing marijuana, it seems Mexican drug lords are still trafficking huge quantities of weed.

Mexican authorities seized more than 45 tons of marijuana last week in Tijuana, a huge bust that suggests pot is still a cash crop for the country's drug cartels despite an increasing number of US states legalizing the drug for recreational and medicinal use.

On June 10, members of the Mexican military and state police acted on an anonymous tip and stopped Francisco Pineda Villanueva and Blanca Estela Robles Garcia as they drove through the Baja California border town in a Honda CR-V, according to local news site AFN Tijuana. A search of the vehicle reportedly turned up 54 kilos of weed, and the couple allegedly admitted under questioning that they worked as guards at a warehouse where a much larger stash could be found.

On June 12, after obtaining a search warrant, military personnel surrounded a warehouse in Granjas Familiares, a sparsely populated area southwest of Tijuana. The soldiers reportedly found 5,271 packages of high quality pot wrapped in brown tape hidden in an underground room. The haul tipped the scales at a whopping 41.6 metric tons (more than 91,700 pounds, or 45.8 tons), the biggest seizure in Baja California since authorities confiscated a record load of 134 metric tons in 2010.

The packages were reportedly marked with 15 different logos and signs, including the Looney Tunes character Road Runner, which could help authorities figure out where the marijuana came from and where it was going. According to unofficial information gathered from local Tijuana news outlets, Sinaloa cartel kingpin Ismael "El Mayo" Zambada is the suspected owner of the warehouse.

Several reports have suggested that marijuana legalization in the US, where 23 states and Washington, DC now have laws that allow some form of legal weed, has been bad for business for Mexican cartels. According to the United Nations, a third of marijuana consumed in the US is now grown domestically — up from just a sixth in years past. US pot is typically far more potent than the Mexican product, which is usually grown outdoors and packaged in tight bundles that users derisively refer to as "brick weed."

But while American demand for Mexican mota is supposedly plummeting, raids on large-scale marijuana operations still remain common in Tijuana, which is a major transit point for drugs due to its proximity to San Diego and the US border. Around this time last year, Mexican officials seized another 44-ton shipment in the Granjas Familiares neighborhood. Again, the packages were marked with around 15 different symbols and logos.

And not everyone is convinced that the dip in cross-border demand for marijuana could significantly harm the cartels. Adam Isacson, senior associate at the Washington Office on Latin America, a policy group, told Bloomberg that some Mexican farmers are replacing their crops with poppies in order to cultivate heroin. According to a 2013 DEA report, half of the heroin used in the US now comes from Mexico, almost quadruple the amount reported in 2008.

Mexican authorities have arrested multiple high-profile drug lords in recent years, including Sinaloa cartel kingpin Joaquin "El Chapo" Guzman last year and Knights Templar leader Servando "La Tuta" Gomez a few months ago. At an anti-drug trafficking conference in Colombia last week, Tomas Zeron, Mexico's chief criminal investigator, told the Mexican news magazine Procesothat authorities have identified only two cartels still in operation: Zambada's Sinaloa cartel, and the upstart Jalisco New Generation cartel. Zeron also noted that "hundreds" of independent cartel cells are still active.

Zeron's assertion about two remaining cartels contradicted information released a month ago by Mexico's attorney general's office, which claimed that nine cartels are in fact "active threats in Mexico."